1. Field of the Invention
This invention relates in general to the electrical switching of signals and power in microelectronics circuits.
2. Description of the Related Art
Relays generally use a relatively small electrical current to switch a larger one. Relays usually are operated by electromagnetic solenoids: these are difficult to manufacture in very small size.
Relays are of several kinds. AC, DC, latching and non-latching, multiple or single pole.
Solid state relays exist. In these a voltage controls whether a circuit is conductive or not. These are made as microelectronic components. The disadvantage is that a voltage drop occurs across the component such that it consumes power even when inactive. It works only when electrical voltage is applied.
A relay has two circuits, one that operates the actuator and another that acts as a conductive path for power to be used elsewhere.
A relay requires an actuator, making it different from a switch that may be manually operated. Conventional macroscopic relays use solenoids. Miniature relays use electrostatic, piezoelectric, and thermal actuators. Two types of thermal actuators exist: those based on differential thermal expansion, and those utilizing shape memory alloys. It is known that shape memory alloy actuators have higher work output per unit mass than other actuators.
It is a general object of the invention to provide new and improved devices and methods for switching electrical signals in microelectronics applications. Other objects of the invention are to make a microrelay that can be microfabricated in arrays, which latches so that power is not consumed most of the time, has near zero insertion loss, conducts relatively large current, and can be manufactured inexpensively in large volume.
Another object is to fill the great demand which exists to switch high currents in excess of 1 ampere.
Another object is to provide MEMS microrelays which can give engineers and designers a new cost-effective option for use in telecommunications, aerospace automated test equipment, and other applications in various emerging markets.
Another object is to provide MEMS microrelays which can be batch fabricated on a silicon wafer using MEMS technology, thus making them mass producible and inexpensive.
In the invention microfabrication techniques used for the fabrication of microelectro-mechanical systems (MEMS) coupled with sputter deposited thin film shape memory alloy (SMA) actuation technology provide novel means of mass producing arrays of high current carrying microrelays.